The present invention relates to a method and arrangement for controlling an automatic transmission of a motor vehicle driven by means of an internal-combustion engine, the internal-combustion engine being influenceable by a power control element, preferably an accelerator pedal or a throttle valve, and ratios of the transmission are automatically selected at least as a function of the position of the power control element and of the rotational engine speed.
As a rule, automatically shifting, stepped transmissions determine the transmission gear which is to be engaged from the position of the throttle valve and the rotational speed of the engine by means of characteristic shifting diagrams. The characteristic shifting curves at which a gear is changed and which are contained in the characteristic shifting diagrams are displaced in known further developments of transmissions of this type as a function of various parameters. Thus, it is known, for example, from German Patent Document DE 39 22 051 A1 to change between different characteristic shifting diagrams as a function of a driver's vehicle handling or his actions based on the traffic situation and to thus displace the characteristic shifting curves.
Also, from German publication DE-Z Automobiltechnische Zeitschrift, Volume 9/1992, Pages 428 to 436, it is known to recognize by means of a so-called "road resistance monitoring", also increased road resistances and to call a hill/trailer shifting program as a function thereof. For this purpose, the acceleration when driving with a normal load on a level surface is estimated from the actual engine operating condition. If the actual acceleration is below the thus determined value, the above-mentioned special shifting program is called in which the vehicle is operated at high rotational speeds of the engine.
An object of the invention is to provide a method and an arrangement for controlling an automatically shifting transmission which recognizes all types of road resistance changes and reacts to them as a function of the recognized road resistance.
This and other objects are achieved by the present invention which provides a method for controlling an automatic transmission of a motor vehicle driven by an internal-combustion engine, the internal-combustion engine being influenceable by a power control element, with ratios of the transmission being automatically selected at least as a function of a position of the power control element and of a rotational engine speed, the method comprising the steps of: determining a reaction of the vehicle to the position of the power control element; relating the position of the power control element and a reaction of the vehicle thereto to one another to form a first relationship; determining a deviation of the first relationship from a relationship existing during normal driving of the vehicle on a level surface; and displacing the ratios of the transmission toward higher rotational engine speeds as a function of the deviation. The objects are also achieved by another embodiment of the invention which provides an arrangement for controlling an automatic transmission of a motor vehicle driven by means of an internal-combustion engine, comprising: a first generator that determines a position of a power control element of the internal-combustion engine; a second generator that determines a rotational engine speed of the internal-combustion engine and at least one characteristic shifting diagram for automatic determination of a ratio of a transmission connected behind the internal-combustion engine from the signals of the second generator; a third generator that determines a reaction of the vehicle to the position of the power control element; a first comparator coupled to the first and third generators and that relates the signal for the position of the power control element to the signal for the reaction of the vehicle thereto; a second comparator coupled to the first comparator that determines a deviation of the signal of the first comparator from a signal of the first comparator which exists during a normal drive on a level surface; and a displacing device which acts upon the characteristic shifting diagram to displace the ratios in the direction of higher rotational engine speeds as a function of the deviation.
The objects are also achieved by another embodiment of he present invention which provides an arrangement for controlling an automatically shifting stepped transmission of a motor vehicle driven by an internal-combustion engine, comprising: a first generator that determines a position of a power control element of the internal-combustion engine; a second generator that determines rotational engine speed of the internal-combustion engine; a plurality of characteristic shifting diagrams which cover a range between a consumption-optimal and a power-optimal operation of the internal-combustion engine and by which, at least as a function of the position of the power control element and of the rotational engine speed, ratios are automatically selected, said plurality of characteristic shifting diagrams differing in the position of the characteristic shifting curves at which a change of the ratio takes place; means for determining the relationship of the position of the power control element to the reaction of the vehicle, said means including several characteristic diagrams of which one is used, in accordance with the adjusted ratio, for determination of an intermediate quantity as a function of a change of the vehicle speed and the position of the power control element, means for multiplying the intermediate quantity with a factor which is a function of the driving speed and which continuously reduces the value of the intermediate quantity as the driving speed increases; a first order delay line or so-called PT-1 filter that filters said intermediate quantity; and means for selecting, for the displacement of the ratio, the characteristic shifting diagram to be used according to the filtered intermediate quantity, such that with an increasing intermediate quantity characteristic shifting diagrams are selected which increasingly cover the power-optimal operation.
The objects are achieved by still another embodiment of the present invention which provides an arrangement for controlling an automatically shifting continuous transmission of a motor vehicle driven by an internal-combustion engine, comprising: a first generator for determining the position of a power control element of the internal-combustion engine;
a second generator for determining the rotational engine speed of the internal-combustion engine; a plurality of characteristic shifting diagrams which cover a range between a consumption-optimal and a power-optimal operation of the internal-combustion engine and by which, at least as a function of the position of the power control element and of the rotational engine speed, ratios are automatically selected; means for determining a relationship of the position of the power control element to the reaction of the vehicle, said means including several characteristic diagrams of which one is used, in accordance with the adjusted ratio, for determination of an intermediate quantity as a function of a change of the vehicle speed and the position of the power control element; means for multiplying the intermediate quantity with a factor which is a function of the driving speed and which continuously reduces the value of the intermediate quantity as the driving speed increases; a PT-1 or delay line filter which filters said intermediate quantity; and means for selecting, for the displacement of the ratio, the characteristic control curve to be used according to the filtered intermediate quantity, such that with an increasing intermediate quantity characteristic control curves are selected which increasingly cover the power-optimal operation.
By means of the invention, it is advantageously achieved that reductions of the road resistance, such as driving downhill, as well as increases of the road resistance, such as driving uphill or operating a trailer, are recognized by a single method. In contrast to the state of the art, when road resistances are changed, no fixed special shifting program is called but an engine power is adjusted which is adapted to the existing conditions. Finally, the method according to the invention may be used for all types of transmission; that is, particularly for stepped automatic transmissions as well as for continuous automatic transmissions.
In certain embodiments of the invention, by means of the vehicle acceleration, the reaction of the vehicle is detected which is expected by the driver upon his power demand specified by the position of the power control element. As a result, the invention can largely use known devices and sensors of the vehicle which, as a rule, already exist and can therefore be implemented in a cost-effective and simple manner.
In certain embodiments, the displacement of the ratios are proportioned with respect to the amount and speed according to the determined deviation and the displacement is carried out according to a first order delay or so-called PT1-action. As a result, the power of the engine is particularly well adapted to the difference between the power demand, represented by the position of the power control element, and the power output, that is, the reaction of the vehicle. In the event of small deviations, the ratios are displaced only a little. When the deviation continues to exist, the ratios are slowly displaced further. In contrast, in the case of large deviations, the ratios are displaced immediately and rapidly by large amounts.
The arrangement according to the invention also has all advantages of the method according to the invention. Furthermore, it is distinguished by the simple as well as effective use of a characteristic diagram for representing the comparison between the position of the power control element and the reaction of the vehicle thereto, as well as for determining the deviation of this relationship from the normal relationship. This, in turn, is possible in a particularly simple manner where characteristic diagrams are used anyhow for the changing of the characteristic shifting curves. In this case, no characteristic diagram must be supplemented but as a rule an already existing characteristic diagram must only be modified.
The displacement of the ratio which, as mentioned above, results in an increase of the rotational speed level of the engine, may in the simplest case be implemented as a manipulation of the rotational engine speed used for the determination of the ratio to be adjusted. In this case, the rotational engine speed signal is increased by a proportion which is a function of the deviation and, as a result, a ratio is adjusted which was originally provided as really existing for a higher rotational engine speed. For a stepped transmission, certain embodiments provide several characteristic shifting diagrams and carry out the displacement of the ratio by changing the characteristic shifting diagram according to the deviation. For a continuous transmission which has several characteristic control curves, in certain embodiments the displacement of the ratio is carried out by changing the characteristic control curve according to the ratio. In the case of continuous transmissions, the interpolations may naturally also take place by the deviation between two characteristic control curves, specifically a consumption-optimal characteristic control curve and a power-optimal characteristic control curve.